I spent a couple of hours testing this lens against the 70-200 f2.8 IS and the 70-200 f4 IS, and I have to say that it held its own very well. It may be an exceptional copy, but even pixel peeping I had a tough time distinguishing the 70-300 photos from those of the "L" lenses. I wouldn't have any hesitation taking this lens on a trip where weight is an issue.

I bought this lens from B&H because the reviews suggested that it was nearly the equivalent of the f1.4 version in terms of IQ. However, it wasn't even as good as my 24-105 and wasn't much better than the 24-85. I'm surprised, because the even cheaper 35mm f2 has MUCH better IQ and contrast.

This may not be the best lens for birding lens, but for the megafauna is has excellent reach, IQ, and useability. It's a fantastic lens to hand hold and enables you to get the quick shot. Plus it takeS a 1.4X TC very well. FANTASTIC ALL PURPOSE WILDLIFE LENS!